Libyan authorities have thrown their support behind US efforts to track down the perpetrators of the consulate attack, but well-armed militias, possibly backing Islamists, still lie beyond their control.

Libyan military guards check one of the US Consulate's burnt out buildings during a visit by Libyan President Mohammed el-Megarif, not shown, to the US Consulate to express sympathy for the death of the American ambassador, Chris Stevens and his colleagues in the deadly attack on the Consulate on Tuesday, in Benghazi, Libya, Friday, Sept. 14.

The hunt is on in Libya for those behind the consulate attack that ended with the death of a US ambassador and three consulate staff, but the government's tenuous control raises questions about US and Libyan authorities' chances of success.

Ambassador Christopher Stevens and three colleagues were killed on Sept. 11 when an angry protest at the US consulate in Benghazi over a film insulting the prophet Muhammad morphed into a deadly rocket attack. It’s unclear whether the escalation was spontaneous or orchestrated, as some US officials suspect, and whether security lapses by American or Libyan authorities played a role. Most important, the perpetrators remain unknown.

Determining any of that will be hard, especially amid the challenge posed by Libya's numerous militias, which have a host of competing agendas. The good news for investigators is that most Libyans reject the violent ideology that US officials believe fueled the attack, and are unlikely to shelter its perpetrators. Libyan officials have condemned the attack and shown every sign of wanting to work with the US.

Yesterday Libyan authorities said they had arrested and were interrogating four men suspected of involvement in the attack.

But the fledgling government is vastly outgunned by local militias that arose last year to overthrow Muammar Qaddafi and have since refused to lay down their arms. Tripoli has little choice but to seek their help in keeping the peace.

Some Libyan officials suspect those militias’ loyalty. Deputy Interior Minister Wanis Sharif told The New York Times that while the initial assault on the consulate was chaotic, a subsequent attack on a US safe-house appeared planned. He believes the attackers "had infiltrators who were feeding them information.”

“In theory, there was an attempt to bring militias under the control of the interior and defense ministries,” says Wolfram Lacher, a Middle East and North Africa analyst at the German Institute for International and Security Affairs, a foreign policy think tank in Berlin. “But in reality they have kept their own command structures.”

Increasingly, militias – including some with Islamist agendas – are consolidating their power and building up their numbers, Mr. Lacher says. “They want to define the new state by controlling the security sector.”

Some nominally pro-government militias may have betrayed a degree of Islamist sympathy in recent months by permitting ultraconservative Salafi Muslims to attack mosques whose Sufi shrines and graves they called blasphemous.

In the past, US authorities have deployed everything from an alphabet soup of security agencies to cash rewards in efforts to catch suspects in foreign countries, says David Mack, a scholar at the Middle East Institute, a nonprofit research center in Washington, and former US diplomat in several Arab countries, including Libya.

This time the US has publicly ordered FBI agents to Benghazi to help Libyan investigators, and is planning drone flights over northeastern Libya to look for militant Islamist groups some believe carried out the attack.

“It’s not easy,” Mr. Mack says, “It’s one thing if you can get FBI out there, but to a very great degree you have to work with the host government and sources in-country.”

The seemingly mixed loyalties of some militias bodes ill for the government’s ability to help find those responsible for the Americans' deaths.

"On the other hand,” says Mack, “I would guess that they’re far more likely than we are to find Libyans who will talk to them about the perpetrators.”

Strong anti-extremist sentiment

Perhaps aiding the investigation is the fact that there is little support in Libya for the violence on display this week in Benghazi, according to analysts. Many Libyans agree. According to a Gallup poll conducted this spring, 95 percent of Libyans surveyed thought at the time that the militias should be required to turn in their weapons immediately.

Since the attack, demonstrators have taken to the streets of Benghazi and Tripoli to denounce it, declare Islam peaceful, and tell Americans that – in the words of some placards – “We are sorry.”

Similar messages have zipped through Facebook networks around the world. In one video, a series of Libyans – young, old, men, women, chic, modest – recite a simple message in Arabic, in rapid, overlapping cuts:

“I am Libyan, Muslim, against violence, against anarchy, against terrorism, against criminality.”

For Lamia Abusedra, an engineering graduate and culture ministry official who is helping set up a support center for NGOs in Benghazi, her home city, the attack came as a shock.

“People don’t know what to do next,” she says. “They’re talking about how to prevent something like this happening again.”

How receptive locals in Benghazi might be to US investigators is hard to gauge for now, she says, with many emotions running high. Yet some things feel clear.

“We feel that our home has been violated by extremists. And that a guest has been offended on our soil.”